In particular in the aerospace industry, but also in the construction of watercraft and ground vehicles and in the construction of rotors of wind power plants and lightweight structures, fiber composite structures are now indispensable. The fiber-reinforced polymer laminate used in this case may contain carbon fibers, glass fibers, Kevlar, boron fibers or mixed fibers or woven fabric made of the above-mentioned fibers. In this case, the polymer matrix is either formed by “wet” epoxy resins, polyester resins, etc. or “prepregs” which contain resin and woven fabric fibers are used. This is particularly due to the virtually unlimited design possibilities and the enormous saving in weight compared with metal or ceramic materials. By appropriate alignment or material selection of the fiber rovings or fiber mats, i.e. for example a mix of carbon fibers and glass fibers or carbon fibers and Kevlar, in which one type of fiber is used in one direction and the other type of fiber in the other direction or one type of fiber is used inwardly and the other type of fiber outwardly, components constructed from fiber composite material can optimally absorb forces in the predefined manner, i.e. they are optimally adapted to the expected loads and can contribute alone to a considerable weight reduction. One weakness of fiber composite structures is, however, their low delamination resistance or the bond strength of bonds from precisely this material group. Sudden high initial loads can trigger the formation of interlaminar cracks, with relatively little energy being required for the cracks to advance as a result.
It is known in particular in aircraft and ship construction, but also in vehicle manufacture to reinforce carbon-fiber-reinforced plastics material or CFRP skin shells using CFRP stringers, CFRP formers, metal formers and similar structural components in order to withstand the high loads in the main shell region in a weight-optimised manner. Such components can for example be produced by prepreg technology, thermosetting processes or vacuum infusion processes for introducing a matrix, for example an epoxy resin, into reinforcing fibers and subsequently curing in a furnace or autoclave. A fiber composite component is for example composed of reinforcing fibers, whether they are rovings or woven fabric mats. Structural joints, which are intended to have a specific damage tolerance, can be provided with thin metal sheets between abutting surfaces, a transverse reinforcement being added to the fiber composite component by the material thickness of the metal sheet. Various composite technologies have been developed in order to improve the properties in the transverse direction, such as Z-pinning, stitching or tufting.
Furthermore, co-bonding methods are known, in which a fiber composite joining partner is cured in a vacuum in a first step and then, in a second step, the cured first joining partner is connected to a “fresh” joining partner in an integrated manner and cured. For example, in the field of aircraft construction this can be a cured longitudinal reinforcement (stringer) which is connected to the “wet” skin shells of the lower fuselage region of an aircraft structure.
Furthermore, there are also hybrid components which are constructed from a combination of metal or ceramic components with a polymer laminate and can be arranged at different points in the region of an aircraft or spacecraft or of a ground vehicle or watercraft.
WO2011/069899 A2 relates to a method for joining a fiber composite component to a structural component of an aircraft or spacecraft. In this case, a metal film is provided as a transverse reinforcing element between the fiber composite component and the structural component. The metal film is designed to have at least one anchoring element that protrudes at a 90° angle from the surface facing the fiber composite component and is inserted between the fiber composite component and the structural component and integrated therein. Furthermore, a corresponding arrangement is produced according to this method. In this way, it is already possible to achieve an improved delamination resistance of approximately 1.5 kJ/m2 when a titanium film is used as a transverse reinforcing element.